1. Field
Embodiments of the invention relate to a method, apparatus, and computer program product for efficiently communicating feedback in wireless communication systems, and, more particularly, to a code based form of communication between a single mobile station and multiple carriers, such as may operate in a cdma2000 system or similar systems.
2. Brief Description of Prior Developments
3×EV-DV represents an extension of the single carrier 1×EV-DV standard to a standard wherein a single mobile station (MS) can be in simultaneous communication with one, two, or three carriers. One advantageous attribute of 1×EV-DV's robust high-speed downlink data transmission is its ability to dynamically schedule users as a function of the user's received channel quality. In a 1×EV-DV system, each mobile station is in contact with, at most, one carrier at a time. As a result, it is necessary to provide for the acknowledgement/non-acknowledgement of only one received packet at a time.
The multicarrier extension of 1×EV-DV to 3×EV-DV requires the ability of each MS to acknowledge/non-acknowledge (ACK/NAK), via the reverse acknowledgement channel (R-ACKCH), up to three received packets simultaneously.
With reference to FIG. 1, there is illustrated a representative scenario for the spectral relationships of the forward and reverse links of 3×EV-DV used by three nodes and a mobile station. The forward link component of 3×EV-DV is shown in exemplary fashion as employing three forward link spectra 21, 21′, 21″ for forward communication from a node such as a base station to a MS. Each forward link spectrum 21, 21′, 21″ is generally symmetric about a downlink frequency. As used herein, a node may be a base station, another MS, a LAN gateway, or any other transceiving entity within a wireless network that communicates with the MS. Where an entity transmits over multiple antennas, each antenna is considered a node.
In the instance illustrated, the downlink frequencies consist of a central downlink frequency fOD, and two additional downlink frequencies disposed on either side of fOD, at a distance of approximately 1.25 MHz. For the purposes of this description, it is assumed, but not required, that the three downlink spectral bands 21, 21′, 21″ are adjacent. In addition, there is shown a 1×EV-DV reverse link consisting of a reverse link spectrum 23 centered on an uplink frequency fOU.
As is evident, the operational bandwidths across the entire forward link are not symmetric with the reverse link. When seeking to extend the existing 1×EV-DV system to the multicarrier 3×EV-DV system, it would appear at first glance that one might simply linearly extend the 1×EV-DV model by a factor of three. However, it is not desirable to simply triple the reverse link overhead, since the additional reverse link bandwidth would be largely wasted.
What is therefore needed is a method of transmitting received channel quality information over a reverse link from a mobile station to another node in a 3×EV-DV system that does not require a significant increase in transmission overhead beyond that which is required for 1×EV-DV. Preferably, such a method would preserve compatibility with preexisting 1×EV-DV systems. In addition, such a methodology should be extendable to providing for the transmission of multiple data streams from a MS to one or more carriers, such as data streams used to transmit signal quality information. Further, such a technique would minimize, to the extent possible, impact to existing reverse link protocol.